orosslet



L. J. ORO$SLEY.

Microphone No. 233,660. Patented Oct. 26,1880.

llmrn- STATES ATENI LOUIS J. GROSSLEY, OF HALIFAX, ENGLAND.

MICROPHONE.

SPECIFICATION forming part of Letters Patent No. 233,660, dated October 26, 1880.

Application filed December 18, 1879. Patented in England February 1, 1879.

To all whom it may concern:

Be it known that I, LoUIs J OI'IN CRossLEY, of Halifax, in the county of York, England, carpet-manufacturer, have invented a certain improved means or method of transmitting or causing sound by means of an electric current or currents, for the purpose of conveying messages, and for other useful purposes, (English patent dated February 1, 187 9, and sealed April 25,1879,) of which the following is a specification.

The said invention has for its object improve ments in transmitting or causing sound by means of an electric current or curren s, and by employing a compound microphone used in conjunction with a telephone for the purpose of conveying articulated messages, speech, or other sounds, and for other useful purposes, by which means an increase of intensity of sound is produced, conveying faithful, plain, and distinct messages. For this purpose I employ a compound microphone-that is to say, microphones having three, four, or more pencils, and six, eight, or more surfaces teaching each other, by which means the resistance of the circuit is varied, and whether arranged with pencils or of any other form. The compound microphoneis mounted or fitted, by pref erence, on a wood diaphragm, and I find pine wood to answer well; but the microphone may be mounted or fitted on a parchment diaphragm which is stretched or fixed over the top of a drum, box, or other suitable kind of resonant, and diaphragms of any suitable kind of substance may be employed. The compound microphone, when mounted or fitted on a diaphragm, is connected with a battery and induction-coil in such a manner that any variations in the compound microphone caused by soundwaves or by any other means effects a corresponding reaction in the strength of the current of electricity flowing through the compound microphone and induction-coil. The variation also causes a variation in the current induced in the induction-coil connected to a telegraph-line or to any other electrical wires, which cause corresponding currents to flow through the telegraph or electrical wires, and by attaching a telephone to the distant end of the telegraph or electrical wires cause, by the increase of the intensity of the sound produced,

the messages con veyed to be faithfully, plainly, and distinctly heard and recorded; but in order to enable my improvements to be better understood I will proceed to describe the same by reference to the accompanying drawings, in which Figure 1 represents a plan of a compound microphonehavingfour pencils, eight surfaces, and four carbon blocks, the microphone being mounted on a wood diaphragm; Fig. 2, sectional elevation of the same. Fig. 8 represents a plan of a compound microphone with four carbon blocks fitted with four strips of thin copper instead of the carbon pencils; Fig. 4, sectional elevation of the same. Fig. 5 represents a microphone and telephone connected in circuit with a battery and induction-coil. Fig. 6 represents the joining up between two stations with compound microphones and telephones connected in circuit with batteries and induction-coils.

Similar letters of reference are used to represent similar parts.

Figs. 1 and 2 in the accompanying drawings represent a compound microphone in which four pencils ofca-rbon, A B D E, are held loosely in four carbon blocks, F G H I. The microphoneis mounted, by preference, upon a piece of wood or diaphragm, J, and I find pine wood under certain circumstances to answer well and produce better articulation than other kinds of wood when used for this purpose. The microphone is inclosed by a wooden rim, K, and a cover, L, may be fitted over the top of the rim, and made by preference of thin wood; or the microphone may be left open.

I may construct the compound microphone without carbon pencils, which may be replaced by other suitable substances capable of varying the resistance of an electric circuit in a similar mannerto the pencils and carbon blocks, Figs. 3 and 4. In the carbon blocksF G H 1, I fit thin metal strips M, by preference of copper or other light substance. The strips are mounted on four pillars, O, and to each end of the strips I fix a small piece of carbon, 1?, or other substance capable of varying the resistance of the circuit in a similar manner to the pencil-points hereinbefore described. I may lit or mount the compound microphone on a parchment diaphragm, which 1s stretched or fixed over the top of a drum, box, or other suitable kind of resonantmaterial, and diaphragms of any other suitable substance may be employed. I may also construct compound microphones joined up in a line, and also constructed with more than fourpencils and blocks.

The compound microphones having a greater number of vibrating points, and consequently a greater number of points in which the resistance of the circuit is varied,produce louder and more distinct articulated sounds, and are not liable to get out of adjustment like the microphones heretofore employed, in which the articulation is frequently imperfect.

Fig. 5 represents a compound microphone and telephone connected in circuit with a battery and induction-coil. One of the carbon blocks, I, is connected with a battery, Z (J, and another block, F, is connected with the primary wire I? of an induction-coil, Q, the other end being connected by a wire, R, to the battery Z C. One side of the secondary wire is connected by electrical wires S to a distant telephone, T, and the other end of the secondary wire U to earth V or to a return-wire. The compound microphone and induction-coil can be joined up in many varied ways, WhlGlLjO'liling is well known to electricians, and the induction-coil need not be of the simple form shown, but may be varied, and two, three, or more induction-coils may be joined up in circuit, or the induction coil or coils may be used in connection with a condenser, and the com pound microphone may be worked without the induction-coil and simply with a battery or magnetic machine or a thermoelectric generator; but I prefer the induction-coil, which produces better results.

Fig. 6 represents the joining up between two stations of compound microphones and telephones connected in circuit with batteries and induction-coils, and for simplicity the switches for bringing the alarm and other parts into circuit are not shown. The plan shows the instruments joined up between two stations, IV and X. One of the carbon blocks, I, of each station is connected with a battery, Z G, and the blocks F are connected with the primary wires 1? of the induction-coils Q. The other ends are connected by wires It to the batteries Z G, and the sides of the secondary wires are connected by electrical wires S to atelephone, T, and the other ends of the secondary wires Uto earth V, or to return-wires. The telephones '1 are connected by means of the line Y.

Having thus described my improvements and the best means I am acquainted with for carrying the same into effect, I would have it understood that I do not confine myself to the precise details shown and described, as they may be varied without departing from the peculiar character ottheinvention, and that I am aware that ordinary microphonesthat is to say, microphones having only one pencil and only two surfaces tbuchin g each other used in conjunction with a telephone and inductioncoilhave been employed, and to these I'lay no claim: but

What I do claim is l. The described construction of compound microphones, the same consisting in arimmed resonant box or drum, J K, the system of carbon blocks F G H I, mounted on the diaphragm and arranged as shown and described, and the system of carbon points connecting with each other and with the blocks, as and for the purpose set forth.

2. In combination with the rimmed box or drum and its resonant diaphragm, and with the system of carbon' blocks mounted on the diaphragm, the system of thin metal plates M, each having a piece of carbon at each end and the whole applied and arranged substantially as shown and described.

LOUIS JOHN OROSSLEY.

Witnesses:

WALTER J AS. TURNER, EDWARD CLEGG. 

